When comparing Mutt vs sup, the Slant community recommends Mutt for most people. In the question“What are the best command-line email clients for Linux?” Mutt is ranked 1st while sup is ranked 4th.
Ranked in these QuestionsQuestion Ranking
Pro Terminal based
Pro Small and efficient
Pro Threads emails
Pro Active development
Even though it was first released in 1995, Mutt still enjoys an active community following it and having new releases constantly.
Pro Highly Configurable Macros
Sup's features can be extended through extensions developed by the community.
Pro Supports a large number of emails
Sup describes itself as "a console-based email client for people with a lot of email" and rightly so. The hierarchical interface that sup provides and support for tags allows users to easily manage and navigate a large number of emails.
It runs inside the terminal so it doesn't display HTML email, fonts, or graphical elements.